Function git_merge_file 

pub unsafe extern "C" fn git_merge_file(
    out: *mut git_merge_file_result,
    ancestor: *const git_merge_file_input,
    ours: *const git_merge_file_input,
    theirs: *const git_merge_file_input,
    opts: *const git_merge_file_options,
) -> c_int